Hello Natasha,
Water soluble fluxes are indeed safe with SMD assemblies. Typical in-line
cleaners are capable of overcoming the capilary forces you describe,
flushing the contaminated solution out from beneath the component with D.I.
water.
As far as "saponified resin flux and an organic acid flux", you are getting
some terms a bit confused! Rosin flux is commonly made of tree sap and
isopropyl alcohol. It is not "water soluble" but water can be "modified"
with an alkili (saponifier) to cause a process called "saponification" which
causes the fatty acid to become a surfactant (soap). Organic acid is an old
term now more commonly referred to as water soluble. This was because the
original formula was indeed an organic acid. Nowadays, there are all kinds
of synthetic things used and not all are organic, etc.
BTW, another term you might want to modify a bit is "water soluble
solder"... no such thing! There are water soluble fluxes, and these might be
contained in water soluble solder paste used in the SMT assembly process,
but solder is typically a metal alloy, and although can be solublized in
water over very long periods of time, is generally not considered water
soluble!
My opinion on ROSE testing is quite simplistic. Most folks don't test
whatsoever, and an "approximated thumbnail sketch" is worth a thousand
words. It is better to correlate IC/Rose than to never have tested at all.
One company I represent(Austin American Technologies) builds batch cleaners
suitable for your purposes. Please visit www.aat-corp.com and click on the
used equipment link, you might find it very interesting. If you have any
questions, I'd be glad to answer them for you offline.
Regards,
Ed Popielarski
QTA Machine
27291 Jardines
Mission Viejo, Ca. 92692
Phone:949-581-6601
Fax: 949-581-2448
Cel: 949-337-2578
WWW.QTA.NET
Original Message:
------------------------------
Date: Thu, 28 Aug 2003 13:12:12 +1000
From: Natasha Erker <[log in to unmask]>
Subject: Water Soluble Solder and Cleaning Methods
** Proprietary **
Hi all,
I'm new to this list, and would firstly like to say how enjoyable and
informative it is reading all of your comments! I'm hoping that someone
can help to shed some light on the topic of water soluble solders and
cleaning methods. I've been doing a lot of reading on this topic, but
it's all really a lot of information.
Please forgive me if some of my questions sound stupid, but I have very
little experience in this area, and a process engineer I am not!
A bit of background: We currently use no-clean solder on a particular
assembly. Unfortunately, this assembly requires conformal coating, and
it does not adhere sufficiently to the no-clean flux residues.
Therefore, we wish to make the move to a water soluble solder. We only
produce small quantities of these assemblies (~350 per week) and do not
wish to spend a small fortune on the transition.
1) Are water soluble solders safe to use with surface mount devices? As
far as I can tell, they have mostly been used with through hole, as the
small gap of SMD does not allow water to penetrate it when cleaning, and
thus the highly corrosive residues remain trapped beneath.
2) What is the difference between a saponified resin flux and an
organic acid flux? What other types of fluxes do WS solders use? Which
is preferable?
3) Will ionic cleanliness testing provide an indication if the cleaning
process is effective? I believe that ROSE testing is not directly
aplicable to non-rosin based fluxes, but would ROSE, in conjunction with
Ion Chromatography provide useful data? How would be best to monitor the
cleaning process to ensure it is in control?
4) What types of batch cleaners are available? Will an industrial dish
washer provide sufficient pressure to clean SMD with WS solder
assemblies? What price range would I be looking at for an 'effective yet
cheap' cleaner?
I really do appreciate any assistance or guidance! Thanks in advance,
and I look forward to your replies!
Kind Regards,
NaTasha Erker
Compliance Co-ordinator
Crystalaid Manufacture
[log in to unmask]
Kind Regards,
NaTasha Erker
Compliance Co-ordinator
Crystalaid Group of Companies
171 Robertson Street
Fortitude Valley QLD 4006
AUSTRALIA
PH: +61 7 3872 7719
FX: +61 7 3257 1693
email: [log in to unmask]
web: www.crystalaid.com
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